Optical probe and optical pick-up apparatus

ABSTRACT

Disclosed is an optical probe for obtaining a micro spot light, comprising a rod-like glass body having a rectangular cross section as a core for propagating an light wave. The distal end portion of the glass body is gradually diminished toward the distal end so as to form a micro distal end face having a small diameter. The side surface of the distal end portion of the glass body in a direction perpendicular to the polarized direction of the light wave is coated with a light absorber formed of a metal film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of application Ser. No. 09/949,648filed on Sep. 12, 2001. Further, this application is based upon andclaims the benefit of priority from the prior Japanese PatentApplication No. 2000-277109, filed Sep. 12, 2000, the entire contents ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical probe for obtaining a microlight spot and an optical pick-up apparatus using said optical probe.

2. Description of the Related Art

In recent years, an optical probe utilizing an optical near field isused for recording information in an optical disk with a resolution nothigher than the diffraction-limited of light or for observing thesurface of an object to be measured, as disclosed in, for example,publication 1 (S. Mononobe et al.: “Reproducible fabrication of a fiberprobe with a nanometric protrusion for near-field optics”, Appl. Opt.,Vol. 36, No. 8 (11997) pp. 1496–1500) and publication 2 (Y. Kim et al.;“Fabrication of micro-pyramidal probe array with aperture for near-fieldoptical memory applications”, Jpn. J. Appl. Phys., Vol. 39, No. 3B(2000) pp. 1538–1541). In this optical probe, the distal end side of anoptical fiber is sharpened and the side surface the distal end portionis coated with a metal so as to confine the light wave in a micro regionso as to obtain a micro spot.

However, the optical probe of this kind gives rise to the problem that,because of the absorption by the metal coated on the side surface, thelight throughput efficiency is very low. It is certainly possible toavoid the absorption loss, if the metal coating is not applied to theside surface. In this case, however, the oozing of the light wave fromthe sharpened distal end portion of the optical fiber is increased,resulting in failure to obtain a micro spot.

As described above, the conventional optical probe having a metalcoating applied to the side surface of the sharpened distal end portionof an optical fiber gives rise to the problems that the throughputefficiency of the light passing through the probe is very low and thatit is impossible to obtain a desired micro spot unless the metal coatingis not applied to the side surface.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide an optical probecapable of confining the light wave to a core portion so as to make thespot diameter very small and capable of sufficiently increasing thethroughput efficiency of the light wave passing through the coreportion.

Another object of the present invention is to provide an optical pick-upapparatus for performing the recording in an optical disk and forobserving the surface of a target to be observed by using the opticalprobe referred to above.

According to a first aspect of the present invention, there is providedan optical probe for guiding an light wave in a predeterminedpropagating direction and outputting a predetermined component of thelight wave, the optical prove being located in the atmosphere,comprising:

a core configured to transmit the light wave, having a first refractiveindex, comprising a base portion, and a end portion having a end faceand first and second side surfaces, the end portion being graduallydiminished from the base portion to the end face, the first side surfacebeing inclined to a first direction perpendicular to the predeterminedpropagating direction and the second side surface being inclined to asecond direction perpendicular to the first direction and thepredetermined propagating direction; and

a light absorbing layer formed on the first side surface of the core,the second side surface being exposed to the atmosphere, the light wavebeing confined in the end portion, a part of the light wave beingabsorbed in the light absorbing layer, and the predetermined componentpenetrating the end face.

According to a second aspect of the present invention, there is providedan optical probe for guiding an light wave in a predeterminedpropagating direction and outputting a predetermined component of thelight wave, the optical prove being located in the atmosphere,comprising:

a core configured to transmit the light wave, having a first refractiveindex, comprising a base portion, and a end portion having a end faceand first and second pairs of opposing side surfaces, the end portionbeing gradually diminished from the base portion to the end face, theopposing side surface of the first pair being inclined to each other andspaced apart in a first direction perpendicular to the predeterminedpropagating direction, and the opposing side surface of the second pairbeing inclined to each other and spaced apart in a second directionperpendicular to the first direction and the predetermined propagatingdirection;

a light absorbing layer formed on the opposing side surface of the firstpair, the opposing side surface of the second pair being exposed to theatmosphere, the light wave being confined in the end portion, a part ofthe light wave being absorbed in the light absorbing layer, and thepredetermined component penetrating the end face.

According to a third aspect of the present invention, there is providedan optical probe for guiding an light wave in a predeterminedpropagating direction and outputting a predetermined component of thelight wave, comprising:

a core configured to transmit the light wave, having a first refractiveindex, comprising a base portion, and a end portion having a end faceand first and second side surfaces, the end portion being graduallydiminished from the base portion to the end face, the first side surfacebeing inclined to a first direction perpendicular to the predetermineddirection and the second side surface being inclined to a seconddirection perpendicular to the first direction and the predeterminedpropagating direction;

a light absorbing layer formed on the first side surface of the core;and

a transparent cladding layer having a second refractive index lower thanthe first refractive index of the core, and formed on the second sidesurface of the core, the light wave being confined in the end portion, apart of the light wave being absorbed in the light absorbing layer, andthe predetermined component penetrating the end face.

According to a fourth aspect of the present invention, there is providedan optical probe for guiding an light wave in a predeterminedpropagating direction and outputting a predetermined component of thelight wave, comprising:

a core configured to transmit the light wave, having a first refractiveindex, comprising a base portion, and a end portion having a end faceand first and second pairs of opposing side surfaces, the end portionbeing gradually diminished from the base portion to the end face, theopposing side surface of the first pair being inclined to each other andspaced apart in a first direction perpendicular to the predetermineddirection, and the opposing side surface of the second pair beinginclined to each other and spaced apart in a second directionperpendicular to the first direction and the predetermined propagatingdirection;

a light absorbing layer formed on the opposing side surface of the firstpair; and

a transparent cladding layer having a second refractive index lower thanthe first refractive index of the core, and formed on the opposing sidesurface of the second pair, the light wave being confined in the endportion, a part of the light wave being absorbed in the light absorbinglayer, and the predetermined component penetrating the end face.

In an embodiment of the present invention, it is desirable for theoptical probe to be constructed as follows:

(1) The light absorber should be formed of a metal film.

(2) The core should be formed of a dielectric material.

(3) The core should be formed of a semiconductor material.

(4) The core should be prepared by processing the distal end portion ofa rod-like optical guide such that the cross section of the distal endportion is gradually diminished toward the distal end from a baseportion of the optical guide to form a pyramidal configuration, and theinclined side surface of the pyramidal distal end portion is coated withthe light absorber.

(5) The end face of the distal end portion of the core should be shapedrectangular. The end face have first and second pairs of opposing sides,wherein the opposing sides being of the first pair are substantiallyparallel in the polarized direction of the light wave, the opposingsides of the second pair are substantially perpendicular to thepolarized direction of the light wave, and a first width of the firstside is shorter than a second width of the second side.

According to a fifth aspect of the present invention, there is providedan optical pick-up apparatus for searching a target with a predeterminedoptical component, comprising:

a light source configured to generate an light wave having thepredetermined optical component;

an optical probe configured to guide an light wave in a predeterminedpropagating direction and outputting the predetermined component of thelight wave to the target, the optical prove being located in theatmosphere, including:

a core configured to transmit the light wave, having a first refractiveindex, comprising a base portion, and a end portion having a end faceand first and second pairs of opposing side surfaces, the end portionbeing gradually diminished from the base portion to the end face, theopposing side surface of the first pair being inclined to each other andspaced apart in a first direction perpendicular to the predeterminedpropagating direction, and the opposing side surface of the second pairbeing inclined to each other and spaced apart in a second directionperpendicular to the first direction and the predetermined propagatingdirection;

a light absorbing layer formed on the opposing side surface of the firstpair, the opposing side surface of the second pair being exposed to theatmosphere, the light wave being confined in the end portion, a part ofthe light wave being absorbed in the light absorbing layer, and thepredetermined component penetrating the end face to the target, and thepredetermined component being reflected from the target and guided intothe optical probe through the end face of the core; and

a sensing section configured to sense the predetermined componentemerged from the probe.

According to a sixth aspect of the present invention, there is providedan optical pick-up apparatus for searching a target with a predeterminedoptical component, comprising:

a light source configured to generate an light wave having thepredetermined optical component;

an optical probe configured to guide an light wave in a predeterminedpropagating direction and outputting the predetermined component of thelight wave to the target, including:

a core configured to transmit the light wave, having a first refractiveindex, comprising a base portion and a end portion having a end face andfirst and second pairs of opposing side surfaces, the end portion beinggradually diminished from the base portion to the end face, the opposingside surface of the first pair being inclined to each other and spacedapart in a first direction perpendicular to the predetermined direction,and the opposing side surface of the second pair being inclined to eachother and spaced apart in a second direction perpendicular to the firstdirection and the predetermined propagating direction;

a light absorbing layer formed on the opposing side surface of the firstpair; and

a transparent cladding layer having a second refractive index lower thanthe first refractive index of the core, and formed on the opposing sidesurface of the second pair, the light wave being confined in the endportion, a part of the light wave being absorbed in the light absorbinglayer, and the predetermined component penetrating the end face to thetarget, and the predetermined component being reflected from the targetand guided into the optical probe through the end face of the core; and

a sensing section configured to sense the predetermined componentemerged from the probe.

The optical pick-up apparatus is constructed such that a lens and a halfmirror are arranged on the side of the proximal end of the opticalprobe. The light wave emitted from the light source is reflected by thehalf mirror so as to be collected through the lens on the optical probeon the side of the proximal end. Also, the light wave emitted from theproximal end of the optical probe passes through the lens and the halfmirror so as to be collected on the light receiving section.

According to the present invention, a light absorbing film is formed onthat side surface of the core which is substantially perpendicular tothe polarized direction of the light wave propagated through the core soas to eliminate the oozing of the light wave in the particulardirection, thereby obtaining a micro spot light. Further, a transparentclad region is formed on that side surface of the core, which isparallel to the polarized direction of the light wave propagated throughthe core so as to increase the light throughput efficiency. In addition,the object of the present invention can be effectively achieved byeffectively utilizing the construction that the TM mode and the TE modediffer from each other in the propagation loss relative to the presenceof the light absorbing film and in the size of the spot diameter. Itfollows that it is possible to make the spot diameter very small and toincrease the throughput efficiency of the light wave passing through thecore.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is an oblique view schematically showing the construction of anoptical probe according to a first embodiment of the present invention;

FIG. 2 is a graph exemplifying the calculation of the propagation losscaused by a glass/Au light waveguide;

FIG. 3 is a graph exemplifying the calculation of the spot diameter inthe glass/Au light waveguide;

FIG. 4 is a graph exemplifying the calculation of the spot diameter inthe glass/air light waveguide;

FIG. 5 is an oblique view schematically showing the construction of anoptical probe according to a second embodiment of the present invention;

FIG. 6 is a graph exemplifying the calculation of the propagation lossin the glass/Al light waveguide;

FIG. 7 is a graph exemplifying the calculation of the spot diameter inthe GaP/Al light waveguide;

FIG. 8 is a graph exemplifying the calculation of the spot diameter inthe GaP/air light waveguide;

FIG. 9 schematically shows the construction of a pick-up apparatusaccording to a third embodiment of the present invention; and

FIG. 10 is an oblique view schematically showing the construction of anoptical probe according to a modified embodiment of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Some embodiments of the present invention in respect of an optical probeand an optical pick-up apparatus using the optical probe will now bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is an oblique view schematically showing the construction of anoptical probe according to a first embodiment of the present invention.

A reference numeral 10 shown in FIG. 1 represents a rod-like glass corerectangular in cross section, in which a light wave is guided. Thedistal end portion of the glass core 10 is worked pyramidal such thatthe distal end portion is gradually diminished from a rectangular baseportion 14 of the core 10. The core 10 has a micro distal end facesection 11 which is a rectangular shape. The micro distal end facesection 11 has a first pair of opposing sides extending in the polarizeddirection I of the light wave propagated through the core 10 and alsohas a second pair of opposing sides extending in a directionperpendicular to the polarized direction of the light wave. The opposingsides of the first pair have a first width W1 which is not larger thanhalf the wavelength λ/2 of the light wave or within a range between thehalf the wavelength λ/2 and the wavelength λ, for example of 50 nm, andthe opposing sides of the second pair have a second width W2, forexample of 200 nm.

The pyramidal distal end portion of the glass core 10 has four sidesurfaces 12A to 12D. The two side surfaces 12A and 12B having a sameshape and same size, are inclined to each other and spaced apart in thepolarized direction I of the light wave propagated through the core 10.Each of the side surfaces 12A and 12B is coated with a light absorbingfilm 13 formed of a metal film. The other two side surfaces 12C and 12Dhaving a same size and shape, are also inclined to each other and arespaced apart in a direction perpendicular to the polarized direction ofthe light wave. The side surfaces 12C and 12D are not coated with thelight absorbing film and are contacted to transparent clad regions,respectively. In the glass core 10 shown in FIG. 1, the side surfaces12C and 12D are exposed to an atmosphere such as an air, a gas or anoil. In other words, formed is a clad of the air layer, the oil layer orthe gas layer having a refractive index lower than that of the glasscore 10.

In the optical probe as shown in FIG. 1, an light wave is transferred inthe core 10 and guided in the pyramidal distal end portion of the glasscore 10. Thus, the light wave is confined in the distal end portion ofthe core 10 and a part of the light wave is absorbed in the absorbingfilm 13 so that a predetermined component of the light wave penetratesthe end face section 11 to form a micro spot on a target (not shown),for example, an optical disk.

In manufacturing the optical probe of the construction described above,the pyramidal distal end portion of the glass core 10 can be formed byetching or polishing the distal end portion of a glass rod having arectangular cross section. Also, an optical fiber available on themarket can be used as the glass rod.

In the optical probe shown in FIG. 1, the light absorbing films areformed on only the side surfaces inclined to the polarized direction ofthe light wave propagated through the glass core 10. The particularconstruction permits markedly diminishing the loss of the light wavepassing through the optical probe. The principle of the particulareffect will now be described.

FIG. 2 is a graph exemplifying the calculation of the propagation loss α(cm⁻¹) of the planar light waveguide formed of a glass core 10 and ametal clad 13. The graph covers the case where gold (Au) is used as themetal forming the light absorption film 13. As apparent from FIG. 2, ifthe wavelength within the core 10, i.e., the core 10 width W (nm), isrendered not larger than the half wavelength λ/(2n), where n representsa refractive index, which is 1.5 (n=1.5) in the case of glass, thepropagation loss of the TE mode is rapidly increased. This is becausethe ratio of the oozing of the light waveguide mode into the metal isrendered large, with the result that the influence given by theabsorption by the metal is increased. In this region, the light wave isscarcely propagated in the TE mode.

On the other hand, the propagation loss in the TM mode is notappreciably increased even if the core 10 width is not larger than thehalf wavelength. As a result, the increase in the loss for the TM modeis not prominent even if a metal is present.

FIG. 3 is a graph exemplifying the calculation of the spot diameter ofthe propagated light wave in respect of the light waveguide constructedas shown in FIG. 2. What should be noted is that the spot diameter ofthe TE mode is increased in the region where the core width is notlarger than 50 nm, whereas, the spot diameter of the TM mode is notincreased.

FIGS. 2 and 3 support that, in the region of the micro core width, thespot diameter of the TM mode is small, and the propagation loss issmall.

In the first embodiment shown in FIG. 1, which utilizes thecharacteristics noted above, a metal coating 13 is applied to only theside surfaces 12A, 12B inclined to the polarized direction of the lightwave so as to suppress the increase in the absorption loss in thisconfiguration in which the light wave is guided in the TM mode. Since ametal coating 13 is not applied to the side surfaces 12C, 12D inclinedto a direction perpendicular to the polarized direction of the lightwave so as to suppress the increase in the absorption loss in thisconfiguration in which the light wave is guided in the TM mode.Incidentally, it is impossible to obtain a sufficiently small spot inthe direction of the TE mode. However, it is possible to obtain a spotdiameter of 400 nm by, for example, setting the micro distal end facesection 11 at about 200 nm.

FIG. 4 is a graph exemplifying the calculation of the spot diameterrelative to a planar light waveguide of a glass core/air clad structure.Where the air forms the clad, it is possible to obtain the minimum spotof 400 nm with the core width of 200 nm in respect of the TE mode, asdescribed above. Also, in the case of a metal clad, it is possible toobtain a spot diameter substantially equal to the core width in respectof the TM mode as shown in FIG. 3. It follows that, if the width in thisdirection is set at 50 nm, it is possible to obtain a spot of 50 nm×400nm with an optical probe having a distal end shape of 50 nm×200 nm. Inaddition, it is possible to realize a probe small in loss.

As described above, when it come to the optical probe according to thefirst embodiment of the present invention, the distal end portion of theglass core 10 is processed pyramidal to form four inclined distal endside surfaces 12A to 12D. In the first embodiment of the presentinvention, two of the four inclined distal end side surfaces 12A to 12D,i.e., the side surfaces 12A and 12B, which are inclined to the polarizeddirection of the light wave propagated through the core 10, are coatedwith the light absorption films 12 formed of metal films so as toeliminate the oozing of the light wave in the direction perpendicular tothe polarized direction noted above, thereby making it possible toobtain a micro spot. Also, the light absorption films 12 are not formedon the other two side surfaces 12C and 12D, which are inclined in thepolarized direction of the light wave propagated through the core 10,and these side surfaces 12C and 12D are in contact with the transparentlayer. It follows that it is possible to increase the light wavethroughput efficiency in the polarized direction of the light wave.Under the circumstances, it is possible to obtain a micro spot light of50 nm×400 nm by setting the shape of the distal end face section 11 at50 nm in the direction perpendicular to the polarized direction of thelight wave propagated through the core 10 and at 200 nm in the directionparallel to the polarized direction noted above. In addition, it ispossible to increase sufficiently the throughput efficiency of the lightwave passing through the core 10.

An optical probe according to a second embodiment of the presentinvention will now be described. Specifically, FIG. 5 is an oblique viewschematically showing the construction of the optical probe according tothe second embodiment of the present invention.

A reference numeral 20 shown in FIG. 5 represents a GaP substrate. Apyramidal projection 24 is arranged as a core in the central portion ofthe substrate 20. A micro face section 21 at the distal end of theprojection (core) 24 is formed rectangular, with the result that fourinclined side surfaces 22A to 22D are formed in the distal end portionof the projection (core) 24. The two side surfaces 22A and 22B of thefour side surfaces 22A to 22D are positioned to cross the polarizeddirection I of the light wave propagated through the projection (core)24. It should be noted that these two side surfaces 22A and 22B and theupper surfaces 26A and 26B of the substrate 20 contiguous to the sidesurfaces 22A and 22B are coated with light absorption films 28 formed ofmetal films. In the embodiment shown in FIG. 5, the light absorptionfilm 28 is formed of aluminum (Al). On the other hand, the otherinclined side surfaces 22C and 22D, which are parallel to the polarizeddirection of the light wave, are not coated with the light absorptionfilm 28 and are in contact with a transparent clad. In this case, theair layer corresponds to the clad. In other words, the clad is formed ofthe air layer having a refractive index smaller than that of the core24.

FIG. 6 is a graph exemplifying the calculation of the propagation lossof a planar light waveguide consisting of the GaP core and the Al clad.The loss of the TE mode is rapidly increased, and the loss of the TMmode is not appreciably increased in the micro core width region, inthis case, too.

FIG. 7 is a graph exemplifying the calculation of the spot diameter ofthe propagated light wave in respect of the construction of a planarlight waveguide consisting of the GaP core and the Al clad. Also, FIG. 8is a graph exemplifying the calculation of the spot diameter of thepropagated light wave in respect of the construction of a planar lightwaveguide consisting of a GaP core and the air clad. As apparent fromFIGS. 7 and 8, the metal clad makes it possible to obtain a spotdiameter substantially equal to the core width in respect of the TMmode, and the air clad makes it possible to obtain a spot diameter ofabout 130 nm relative to the core width of 60 nm in respect of the TEmode.

It follows that it is possible to obtain a micro spot light of 50 nm×130nm by, for example, setting the shape of the micro distal end facesection 22 at a width W1 of 50 nm in the direction parallel to thepolarized direction of the light wave propagated through the projection(core) 24 and at a width W2 of 60 nm in the direction perpendicular tothe polarized direction noted above. As a result, it is possible torealize an optical probe small in loss.

An optical pick-up apparatus according to a third embodiment of thepresent invention will now be described. Specifically, FIG. 9schematically shows the construction of the optical pick-up apparatusaccording to the third embodiment of the present invention.

A reference numeral 30 shown in FIG. 9 represents the optical probeaccording to the second embodiment of the present invention, which isshown in FIG. 5. As shown in the drawing, the optical pick-up apparatusaccording to the third embodiment of the present invention comprises alaser diode (LD) 31 used as a light source, a photodiode (PD) 32 used asa light receiving element, a half mirror 33, a projection 34, acollimate lens 35, and a light collecting lens 36 in addition to theoptical probe 30. A reference numeral 38 shown in FIG. 9 represents atarget to be inspected.

The laser beam emitted from the LD 31 is collimated by the collimatelens 35 and, then, reflected by the half mirror 33 so as to be directedto the projection lens 34. The projection lens 34 serves to converge thecollimated laser beam so as to irradiate the optical probe 30 on theside of the proximal end with the converged laser beam. The convergedlaser beam incident on the optical probe 30 is guided into the inside ofthe probe 30 so as to have its diameter miniaturized and, then, emittedfrom the distal end for irradiation of the surface of the target 38.

A part of the laser beam reflected from the surface of the target 38 isincident on the distal end of the optical probe 30 so as to be guidedwithin the probe 30 and, then, emitted to the outside from the proximalend of the optical probe 30. The laser beam emitted from the proximalend of the optical probe 30 passes through the half mirror 33 and, then,is converged by the convergent lens 36 so as to form an image on thephotodiode (PD) 32.

The signal detected by the photodiode (PD) 32 contains information onthe irradiated surface region on the target 38 and is changed inaccordance with the surface state of the target 38. It follows that itis possible to observe the surface state of the target 38 on the basisof the signal detected by the PD 32 by relatively moving in parallel theoptical probe 30 and the target 38.

The polarized direction of the laser beam emitted from the LD 31 is inthe up-down direction on the paper, and the polarized direction of thelaser beam reflected by the half mirror 33 is in the right-leftdirection on the paper. It follows that the side surfaces of the opticalprobe 30, which are coated with a light absorber 28, are the twoinclined side surfaces 22A and 22B inclined to the polarized direction Iof the laser beam propagated through the projection (core) 24, with theresult that it is possible to converge the light wave into a micro spot.In the apparatus shown in FIG. 9, the laser beam emitted from the LD 31is polarized in the up-down direction on the paper, and the lightabsorber 28 of the optical probe 30 is arranged on the left side surfaceand the right side surface of the projection (core) 24. Where thepolarized direction of the light wave emitted from the LD 31 isperpendicular to the paper, the light absorber 28 should be formed onthe front side surface and the back side surface of the projection 24.

As described above, the optical probe 30 equal to that described inconjunction with the second embodiment of the present invention is usedin the optical pick-up apparatus according to the third embodiment ofthe present invention. In addition, the optical pick-up apparatus isprovided with a mechanism (31, 33, 34, 25) for introducing the lightwave into the optical probe 30 and another mechanism (32, 33, 34, 36)for guiding the light wave out of the optical probe 30. The particularconstruction of the optical pick-up apparatus makes it possible toconverge the light wave irradiating the target 38 into a micro spot andto detect the light wave from the microscopic region on the surface ofthe target 38. It follows that it is possible to perform the recordingwith a resolution not larger than the diffraction-limited of the lightwave and to measure the surface state of target with a high accuracy.

The present invention is not limited to each of the embodimentsdescribed above. In the embodiments described above, the cross sectionof the core portion (the entire core portion in the first embodiment,and the projecting portion of the core in the second embodiment) isshaped rectangular. However, it is possible for the cross section of thecore portion to be shaped circular or elliptical. Where the crosssection of the core portion is shaped circular or elliptical, the metalfilm coating the side surface of the core portion should be formed in aregion facing the polarized direction of the light wave, i.e., thesurface within a range of 90±45° relative to the polarized direction.

Also, the material of the light absorbing film is not limited to goldand aluminum. It is possible to use another metal as far as the lightwave can be absorbed. It is also possible to use a material other thanthe metal. Also, it is not absolutely necessary for the surface otherthan the surface on which is formed the light absorbing film to be incontact with the air. It is possible for the particular side surfaces12A and 12B to be coated with a transparent film 15C and 15D having arefractive index smaller than that of the core, as shown in FIG. 10. Inthis construction as shown in FIG. 10, the rectangular base 14 of thecore 10 is also coated with a transparent film 15 having the refractiveindex smaller than that of the core.

Further, the material of the core is not limited to glass and asemiconductor as far as the core material sufficiently transmits thelight wave. For example, it is possible to use GaN with respect to thewavelength shorter than that in the embodiments described above.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the present invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

1. An optical pick-up apparatus for picking up data from a medium with apredetermined optical component, comprising: a light source configuredto generate a light wave having the predetermined optical component; anoptical probe configured to guide a light wave in a predeterminedpropagating direction and output the predetermined optical component ofthe light wave to the medium, the optical probe being located in anatmosphere, and the light wave being polarized in a first directionperpendicular to the predetermined propagating direction, said opticalprobe comprising: a core configured to transmit the light wave, having afirst refractive index, comprising a base portion and an end portionhaving an end face and first and second opposed surfaces, the endportion being gradually diminished from the base portion to the endface, the first opposed surfaces inclining to the first direction andextending along a second direction perpendicular to the first directionand propagating direction, and the second opposed surface beinginclining to the second direction and extending along the firstdirection; and a light absorbing layer formed on the first opposedsurfaces of the core, the second opposed surfaces being exposed to theatmosphere, the light wave guided in the core being confined in the endportion, a part of the light wave being absorbed in the light absorbinglayer, the predetermined optical component penetrating the end face tothe medium, and the predetermined optical component being reflected fromthe medium and guided into the optical probe through the end face of thecore; and a sensing section configured to sense the guided predeterminedoptical component.
 2. The optical pick-up apparatus optical probeaccording to claim 1, wherein the light absorbing layer is formed of ametal.
 3. The optical pick-up apparatus according to claim 1, whereinthe core is formed of a dielectric material or semiconductor.
 4. Anoptical pick-up apparatus for picking up data from a medium with apredetermined optical component, comprising: a light source configuredto generate a light wave having the predetermined optical component; anoptical probe configured to guide a light wave in a predeterminedpropagating direction and output the predetermined optical component ofthe light wave to the medium, the optical probe being located in anatmosphere, said optical probe including: a core configured to transmitthe light wave, having a first refractive index, comprising a baseportion and an end portion having an end face and first and second pairsof opposed surfaces, the end portion being gradually diminished from thebase portion to the end face, the first and second pairs of opposedsurfaces being extended from the base portion to the end face, the firstpair of the opposed surfaces being inclined to each other, and spacedapart in a first direction perpendicular to the predeterminedpropagating direction, and the second pair of the opposed surfaces beinginclined to each other and spaced apart in a second directionperpendicular to the first direction and the predetermined propagatingdirections; a light absorbing layer formed on the first pair of theopposed surfaces, the second pair of the opposed surfaces being exposedto the atmosphere, the light wave being confined in the end portion, apart of the light wave being absorbed in the absorbing layer, and thepredetermined optical component penetrating the end face to the medium,and the predetermined optical component being reflected from the mediumand guided into the optical probe through the end face of the core; anda sensing section configured to sense the guided predetermined opticalcomponent.
 5. The optical pick-up apparatus according to claim 4,wherein the light absorbing layer is formed of a metal.
 6. The opticalpick-up apparatus according to claim 4, wherein the core is formed of adielectric material or semiconductor.
 7. The optical pick-up apparatusaccording to claim 4, wherein the light wave has a polarized directionand the first direction corresponds to the polarized direction.
 8. Anoptical pick-up apparatus for picking up data from a medium with apredetermined optical component, comprising: a light source configuredto generate a light wave having the predetermined optical component; anoptical probe configured to guide a light wave in a predeterminedpropagating direction and output the predetermined optical component ofthe light wave to the medium, the light wave being polarized in a firstdirection perpendicular to the predetermined propagating direction, saidoptical probe including: a core configured to transmit the light wave,having a first refractive index, comprising a base portion and an endportion having an end face and first and second opposed surfaces, theend portion being gradually diminished from the base portion to the endface, the first and second opposed surfaces being extended from the baseportion to the end face, the first opposed surfaces being inclined tothe first direction and extended along the second directionperpendicular to the first direction and the propagating direction, andthe second opposed surfaces being inclined to the second direction andextended along the first direction; a light absorbing layer formed onthe first opposed surfaces of the core; and a cladding layer having asecond refractive index lower than the first refractive index of thecore, and formed on the second opposed surface of the core, the lightwave being confined in the end portion, a part of the light wave guidedin the core being absorbed in the light absorbing layer, thepredetermined optical component penetrating the end face to the medium,and the predetermined optical component being reflected from the mediumand guided into the optical probe through the end face of the core; anda sensing section configured to sense the predetermined guided opticalcomponent.
 9. The optical pick-up apparatus according to claim 8,wherein the light absorbing layer is formed of a metal.
 10. The opticalpick-up apparatus according to claim 8, wherein the core is formed of adielectric material or semiconductor.
 11. An optical pick-up apparatusfor picking up data from a medium with a predetermined opticalcomponent, comprising: a light source configured to generate a lightwave having the predetermined optical component; an optical probeconfigured to guide a light wave in a predetermined propagatingdirection and output the predetermined optical component of the lightwave to the medium, said optical probe including: a core configured totransmit the light wave, having a first refractive index, comprising abase portion and an end portion having an end face and first and secondpairs of opposed surfaces, the end portion being gradually diminishedfrom the base portion to the end face, the first pair of opposedsurfaces being inclined to each other, spaced apart in a first directionperpendicular to the predetermined propagating direction and the secondpair of opposed surfaces being inclined to each other and spaced apartin a second direction perpendicular to the first direction and thepredetermined propagating directions; a light absorbing layer formed onthe first pair of opposed surfaces; and a cladding layer having a secondrefractive index lower than the first refractive index of the core, andformed on the second pair of the opposed surfaces, the light wave guidedin the core being confined in the end portion, a part of the light wavebeing absorbed in the light absorbing layer, and the predeterminedoptical component being reflected from the medium and guided into theoptical probe through the end face of the core; and a sensing sectionconfigured to sense the predetermined guided optical component.
 12. Theoptical pick-up apparatus according to claim 11, wherein the lightabsorbing layer is formed of a metal.
 13. The optical pick-up apparatusaccording to claim 11, wherein the core is formed of a dielectricmaterial or semiconductor.
 14. The optical pick-up apparatus accordingto claim 11, wherein the light wave has a polarized direction and thefirst direction corresponds to the polarized direction.